Disclaimer
This report was compiled by an ADRC visiting researcher (VR) from ADRC
member countries.
The views expressed in the report do not necessarily reflect the views ofthe ADRC. The boundaries and names shown and the designations usedon the maps in the report also do not imply official endorsement or
acceptance by the ADRC.

TSUNAMI EARLY WARNINGSYSTEM IN JAPAN
Fathmath Shaushan Moosa
Senior Administrative officer
National Disaster Management Centre,
Rep of Maldives

GENERAL INFORMATION| Japan

is an archipelago of6,852 islands.
| Surrounded by the sea| About 73 percent of Japan isforested, mountainous.
| habitable zones, mainly locatedin coastal areas are highly
populated.
| JapanJ- one off thethmostt
populated countries in theworld

CLIMATE| Clear-cut temperature changes

between the four seasons| The
average
wintertemperature is 5.1 °C (41.2 °F)| average summer temperature
is 25.2 °C (77.4 °F).
| Rainey
R iseason begins
b ii earlyinl
May in Okinawa and gradually
moves north until Hokkaido inlate July.
| Latesummer andearly
yautumn - typhoons

NATURAL HAZARDS IN JAPAN| Geographicaland climatologically vulnerable todisasters such as• Typhoon
T h• Torrential Rain
• HeavyHSSnow• Earthquake• Tsunami• Volcanic Eruptions| Located in circum pacific (Ring of fire)| Have the highest natural disaster riskin theddevelopedld worldld

NATURAL HAZARDS IN JAPAN

EARTHQUAKES AROUND JAPAN| Earthquakes

occur because ofplate movement| JapanJiissituated
it t diinasubduction zone
| Pacific
plate and Philippine
plate subduct (North Americanplate and Eurasian plate)severall centimetersti t
annually.
ll| These movement cause forces toact in various directions| Extremely high seismic activity| 1300 – 2000 earthquakes
qare felt
per annum

MEASURING EARTHQUAKE| Two types of waves are

emitted by an earthquake| P-Wave
PW: firstfi t wave tto arrivei• Causes very little or nodestruction| S-WaveSW: travels
tl slowerlththanP-wave• Causes most damage such as
the destruction of buildings
and landslides| efficientearthquake warning
system – quickly detect the Pwaves andd issue
ia warningi
before the arrival of these swaves| A seismograph or seismometeris the measuring instrumentgthat creates the seismogram.

|Aseismogram is a record of
the seismic waves from anearthquake.

SEISMIC INTENSITY ANDMAGNITUDE| Seismicintensity describes
the scale of the groundmotion at a particularlocation.
| Varies with the distance fromthe epicenter| Magnitude is a numericalvalue that represents thescaleofafault
slip
underground| Large earthquakes have highmagnitude
i dTSUNAMI| Seriesof very long waves generated by rapid,
large-scale disturbances of the sea| Displacement
Di lt off a largelvolumeloff water,tgenerally from the raising or lowering of theseafloor caused by:• earthquakes• landslide• volcanic eruptions• explosions• meteorites

| Oncea tsunami has been ggenerated,, its energy
gy is
distributed throughout the water column.
| waves travel outward on the surface of the ocean in
all directions away from the source.
source| The deeper the water, the greater the speed oftsunami waves is.
| But can pass under a ship in the ocean with thoseaboard the vessel hardly noticing| As it reaches the shore it slows down the speed but
increase the high

| Thewave length
gand their pperiod dependpon thegenerating source and the dimension.
| Tsunamis arrive at a coastline as a series ofsuccessive
i crestt andd troughs.
th| Tsunami wave smash into shore like a wall of wateror move ashore as a fast moving flood or tide.
tide| Destroying everything in its path
| Tsunamis stuck with devastating force and reach ahigh of 30 -50 meters.
| Tsunami run-up of more than 1 meter is dangerousdue to the strong force| Greater tsunamis move inland with debris andsometimes with massive fire| Coasts and islands with steep fridges or surroundedy barrier reefs are safer than those with ggraduallyyby
rising fringes or those that are exposed to open ocean

MEASURING TSUNAMI
Tide Gauge

Open ocean buoy

Satellite

Costal Tsunami monitoringsystem

INDIAN OCEAN TSUNAMI| Earthquake of m 9.0 to the western

coast of northern Sumatra| Mega thrust – India plate and Burmatectonic plates| Vertical displacement of the sea-floor
generated the devastating tsunami| 11nations - complete surprise for the people living on
the area – no early warning received| Over 226,000 people are known to have lost their lives| More than 1.5 million people were left homelessaroundd theh regioniGREAT EAST JAPAN EARTHQUAKEQANDTSUNAMI| Earthquake
E thk off m 9.0
9 0 tot hhypocentertat an underwater depth ofapproximately
i t l 30 kmk| Pacific plate dive beneath theEurasian plate releasing built up stress| The countries stringent seismic building code andy warning
gp
prevented it from the worst caseearly| Powerful tsunami wave of 40.5 meters| More than18000 people died of the tsunami –drowning| Tsunami caused level 7 meltdown of Fukushima
Daiichi Nuclear power plant

DATA COLLECTION SYSTEM| 180 seismographs and 600 seismic

intensity meters for earthquake detection| 110 sea level gauges| Tsunami detection buoys| Natural phenomena and weather
conditions are monitored 24 hrs

EARTHQUAKEQINFORMATION ISSUED BY
JMA| EEW are issued after and earthquake occurs| There are no earthquake prediction technology| Provides first announcement by detecting P-Waves| Technology that forecasts from very weak shakingandd communicationi i technology
h lforf prompt
dissemination are the key elements

Title

Content and Timingg to be issued

Seismic Intensity
Information

This information is issued within about two minutes from an earthquake toprovide information on the regions where seismic intensity of 3 or more wasobserved Each prefecture is divided into 2 or more regions.
observed.
regions

Earthquake
I f
Information
tiThe location and magnitude of an earthquake is determined within about
three minutes. In case of no tsunamigenic
gearthquake,q, the message
g of“Tsunami is not expected” is added.

Earthquake andSeismic Intensityy
Information

This information indicates the location of the hypocenter, magnitude, andname of regions,g, cities,, towns and villages
g in which intensityy of 3 or more
was observed.

Information onseismic intensity ateach site

All stations which observed intensity of 1 or more, hypocenter location andmagnitude
i d off theh earthquake
hk are provided.
id dShake Map

Just after an earthquake, the shaking-intensity map is prepared. This map is
produced taking into account local geological conditions and observed
seismic intensity

Information on thenumber ofearthquakes

When earthquakes occur frequently in a same place called earthquake
swarm, hourly/daily number of earthquakes is provided.

RESPONSE TO A EARTHQUAKEQ
EARLYWARNING SYSTEM

LIMITATIONS TO EEW| Timing| False alarm| Magnitude estimation| Seismic intensity estimation| JMA continue improving the accuracy and timingof the EEW through joint research with theNIEDTSUNAMI INFORMATION ISSUED BY JMA|Computer simulations oftsunamis with variousmagnitude and location
are stored in a database|When a large earthquake

occurs the system calculates
Its hypocenter and magnitude searches thedatabase, selects the closest matching result|JMA Issues the warning or advisory

FLOW OF INFORMATION ABOUT
EARTHQUAKE AND TSUNAMITSUNAMI WARNING AND ADVISORIESTSUNAMI INFORMATION
Messages about tsunami

Indication

Estimated arrival times and heights of the tsunami for relevant tsunami
forecast regions.
Tsunami Information* The estimated tsunami arrival time for each tsunami forecast region is(E i(Estimatedd TTsunamii AArrival
i l TiTime anddthe time at which it is expected to hit first in any part of that area.
Height)Hence, in some coastal regions, tsunamis may hit after the estimatedtime.
Tsunami Information
The high tide times and estimated arrival times of the tsunami at(High Tide Time and Estimatedselected points.
Tsunami Arrival Time at each place)
Tsunami Information (*1)
Arrival times and heights of the tsunami observed at tide gauges or(Tsunami Observations)tsunami meters
meters.
Tsunami Information (*2)
Tsunami arrival times and heights observed at offshore gauges, and(Tsunami Observations at Offshore related tsunami heights along the coast in the corresponding forecastGauges)
region estimated from offshore observations.

*1 Issuance of information based on tsunami observation*2 Issuance of information based on Tsunami Observation at off shoregauge

TSUNAMI FORECAST| After an earthquake occurs, if no damage isexpected, JMA issues Tsunami Forecasts.

Forecasted sea level changes

Message

No tsunami is expected"No tsunami is expected." (To be included in Earthquake
Information.)

Tsunami heightg less than 0.2 meters No damage
g is expectedpbecause sea level changes
g will beis expectedless than 0.2 m, and no special action is needed.
Slight sea level changes are expected Particular attention is needed when fishing, swimming or
to cocontinuet ue
eengaginggag g in otherot e marinea e activities
act t es because tsunamitsu aafter Tsunami Warnings/advisories related sea level changes have been observed and may
are cleared
continue for a while.

DATA AND INFORMATION SHARING SYSTEMEARLY WARNING SYSTEMCENTRAL DISASTER PREVENTION RADIONETWORKJ-ALERT SYSTEMDISTANCE EARTHQUAKEQINFORMATION
AND INTERNATIONAL TSUNAMI ADVISORIES| JMA monitors
itseismic
i iactivity around thewoworld| When a large
earthquake occurs near
JJapan,pacificifi region
i orIndian ocean, JMA
provides international
tsunami advisories tothe countries| UsedU d ffor tsunamii
warning andevacuation orders.

RECOMMENDATIONS WHEN DEVELOPINGAN EARLY WARNING SYSTEM| Link with community-based activities| Start with low-cost systems| Conduct Communication drills| Understand the limitations of technology| Guidelines for quick decision making| Understand communities’ coping

mechanisms| Establish uninterrupted systems| Ensure services are available 24/7

THANK YOU